Charge forming device



Oct. 24, 1944. F. c. MocK CHARGE FORMING DEVICE s sheets-'sheet 1 Filed Aug. 5, 1940 IN VEN TOR FQAA/A/ I /Voc/c Q c. @er 2 %Z ATTORNEY Oct. 24, 1944. F, C* MoCK 2,361,227

CHARGE FORMING DEVICE Filed Aug. 3, 1940 '.5 Sheets-Sheet 2 /B 29 5 l D 136 I l [66 l77 C A 64 /73 /ez I ,Isl l I/ l 65 f ff 6 /69 /3/ las o /7/ ,8 /87 nz o 76 58o l 625 o 9 l5 d I9 64 l 20/ /7 l 3 o O F/a 3 o o C IN VEN TOR FFAA/ C. /VQCA/ 62.@ C en 972 ATTORNEY Oct. 24, 1944. F. c. MocK CHARGE FORMING DEVICE Filed Aug. 3, 1940 3 Sheets-Sheet INV/mm2 FRANK C. MocK M a %TTORNEY Patented Oct. 24, 1944 CHARGE FORMING DEVICE I'ank C. Mock, South Bend, Ind., assigner to Bendix Products Corporation, South Bend, Ind.,

a corporation of Indiana Application August s, 1940, serial No. 350,519

(c1. zei- 69) Claims.

This invention relates to charge forming devices of the pressure feed or closed fuel system types and is particularly concerned with the design and/or arrangement of the parts to facilitate assembly and reduce the cost of manufac ture. The invention is also concerned with the provision of means for automatically eliminating air. fuel vapors, and Water from the various chambers of the device and of means for cutting off all fuel flow to the engine when it is to be stopped. The present application is a continuation-in-part of my copending application Serial No. 202,206, filed April 15, 1938.

Charge forming devices of the pressure feed type have certain inherent advantages, as compared to a conventional carburetor, which make them particularly adaptable for use in aircraft, and as a consequence have been largely developed for use in the aircraft engine field. In the past the cost of devices of this type has been relatively high, partially because a relatively small number of each of a multiplicity of models are manufactured. This condition resultsfrom several interrelated factors. The total aircraft engine production, which in its entirety is relatively small, consists of a' moderately large number of engine models of various sizes or designs. As will be apparent to one skilled in the art, each model Vor size of engine requires a more or less modified carburetor, thus the air passages and venturis may be of various sizes or shapes, the fuel control systems may be of various types, or the fuel discharge nozzles may have to be of different forms or differently arranged to produce the desired fuel distribution pattern necessary for satisfactory engine operation.

Furthermore, each model engine may be used in several types of aircraft, for example, a given model might be used in commercial transports, military bombers and pursuit planes, each of which is subjected to an entirely different type of service having diiferent fuel control requirements and requiring a modified carburetor. Also, a particular model engine may be used on aircraft of a given type, such as pursuit planes, but having fuselages built by different manufacturers which require modified carburetor controls or, because of space limitations, variations in the size, shape, or arrangement of the induction passage or other parts of the carburetor. Thus a different carburetor model may be required not only for each engine model but also foreach type of service or make of fuselage in which the engine model is to be used.

The problem of eliminating air, fuel vapor, and

water is present in all the models and provision must therefore be made to eliminate these undesirable fluids if and when they appear. It is furthermore desirable to provide in all models a means for` cutting oi all fuel flow to the engine when it is to be stopped to eliminate the tendency for the engine to continue to run, because of preignition in the engine cylinders,v after the ignition is turned 01T.

From the above factors, it will be readily apparent that a multitude of aircraft carburetor models must be manufactured, each differing from the others in certain respects but having some parts in common with at least a portion of the others. By designing the carburetor so as to consist of several separate units each capable of separate assembly and then assembly with the other units to make up a complete charge forming device, all units that are common to one 0r more models may be manufactured and assembled on one production line, thus decreasing the cost of production. Furthermore, each unit, particularly those having some function which enters into the fuel metering ability of the device, may be individually tested and calibrated before'nal assembly. Variations resulting from manufacturing tolerances which would be difficult to isolate in the complete device may thus be traced to the individual unit before final assembly with other units in making up the complete device.

It is therefore an object of the present invention to provide a charge forming device comprising several separate sub-assemblies.

A further object is to provide a charge forming device in which the parts most likely to be varied for adaptation to various engines or installations are included in separate sub-assem blies of the complete device.

A further object is to provide a charge forming device comprising several separate sub-assemblies which may be individually tested and calibrated.

A further object is to provide means whereby the charge forming device will automatically eliminate air, fuel vapor, and Water from the chambers of the device.

A further objectv is to provide an improved means for cutting olf all fuel flow to the engine when itis to be stopped.

A still further object of the invention is to provide a charge forming device which may be manufactured in a multiplicity of models at reasonable cost.

A still further object is to provide an improved charge forming device of the pressure feed type. Other objects and advantages will be apparent .to one skilled in the art from the following detailed description taken in connection with the appended drawings, in which:

Figure 1 is a top view of a charge forming device embodying the invention, the regulator unit 'thereof being shown in section;

Figure 2 is an elevational view in section, taken on the line 2-2 of Figure 1, showing the throttle body, the automatic mixture control unit, the fuel regulator unit and the adapter section;

Figure 3 is a side elevation of the device of Figure 1 with the fuel control unit sectioned on line 3-3 of Figure 1 and with portions of the regulator unit broken away; 1

Figures 4, 5, 6 and 7 are elevational views of the mixture control valve in its idle cut-off, automatic-lean, automatic-rich and full-rich emergency positions respectively; and

Figure 8 is a diagrammatic view of the entire charge forming device in which the separable units and their interconnecting passageways are shown in a single plane, the units being maintained substantially at their respective levels.

With particular reference to Figures 1, 2, 3 and 8 there is shown a charge forming device of the pressure feed type having ve separate units or sections, a body A, an automatic mixture control unit B, a fuel regulator unit C, a fuel control unit D and a fuel nozzle adapter section E. Each of said units or sections is capable of separate assembly and testing and subsequent attachment to the other units or sections tor make up a complete device.

The body A comprises an induction passage having two barrels, each of which has an inlet I and an outlet I controlled by a throttle I2 secured to a rotatable shaft I3. A flange I at the top of the body A is adapted to have secured thereto a scoop or air entrance section (not shown) which is generally of the elbow type. A large venturi I1 is secured in each of the induction passage barrels and is formed with an annular chamber |8 communicating with the air inlet |0 through tubes I9 which project into the induction passage so as not to transmit to said chamber water or rain which is carried into the scoop and runs down the Walls of the induction passage. Air passages 2|, 22, 23 and 2-4 communicate the chamber I8 with the bottom of a chamber in the regulator unit C, yet to be described. A by-pass 25 connects passages 2| and 24, and has a valve 26 which is closed at all times except when operating in the emergency-rich setting as will be explained hereinafter. Small venturis 29 extend into the venturis I1 and have three prong-like members 30, 3| and 32 secured to the top portion of the body A by screws 33. An annulus 35 opening into the throat of venturi 29 communicates by means of an air passage 36 in the prong-like member 32 with an air passage 31 leading downwardly in the body A. The passage 31 communicates adjacent the bottom thereof with the induction passage posterior to the throttle by means of a restricted bleed 38 and with the lower portionof a chamber of the regulator C, yet to be described, by means of an air passage 39.

The automatic mixture control unit B comprises a base member 42 into which is threaded a cap 43. A sealed chamber having an upper non-deformable portion 44 and a lower deformable bellows portion 45 is threaded into the top of the cap 43 and secured thereto by lock-nut 46. A valve element 41 is connected to the lower movable wall of the bellows to be actuated thereby and is slidably received in a central aperture in the base member `42 for controlling a port 48 forming a communication between air passages 22 and 23. A gasoline-resistant rubberlike seal 49 is provided in a groove on the lower end of base v42 for sealing the base in the passage 22. The internal structure and arrangement of parts of the unit B are more particularly described in my copending application Serial No. 120,654, filed January 15, 1937. Ports 50 and 5| are respectively provided in the base 42 and cap 43 to permit entering air to circulate through the cap 43. The automatic mixture control unit is rst assembled and may be separately tested by subjecting it to various external pressures and checking the needle travel or the rate at which it restricts a master passage in a test fixture. The calibrated unit is then threaded into the body A. The unit B is so designed, as described in the above copending application, that the valve 41 variably restricts port 48 in response to variations in entering air pressure and temperature.

The regulator unit C comprises three mainl castings or sections 54, 55 and 56, the section 56 being provided with two or more studs 51 (Figure 1) which extend through sections 54 and 55 for purpose of separate assembly of the regulator unit. The section 54 has a housing 58 integrally cast therewith which includes a fuel inlet 59 (Figure 3) adapted to receive fuel from a source of fuel under pressure such as a by-pass type constant pressure fuel pump. A cylindrical iilter of fine mesh screen 60 within the housing 58 is urged against 'an annular seat 6| by a spring 62 cooperating with a cap 63. A central bolt 64 secures the cap 63 to the housing, a gasket being provided for purpose of sealing. A vapor outlet 65, adapted to be connected to the fuel tank, is provided in the uppermost portion of housing 58., A float valve indicated generally at 66 controls the vapor outlet. A passage 69 communicates the interior of the cylindrical screen 60 with an annular chamber 10 in a sleeve-like extension 1I of the regulator section 54. 'A shouldered sleeve 12 having a tapered valve seat 13 is secured in the extension 1I by locking nut 14 and packing 15 and is provided with radial apertures 16 closely adjacent the seat 13 which communicate with the annular chamber 10. A tapered valve 19 is slidably received in the sleeve 12 and is carried by a plug 88 threaded on a valve stem 8|. A diaphragm 82 serves to seal the outer end of the valve member to prevent leakage of fuel therepast from the annular chamber 10. The diaphragm preferably has an effective area equal to the area of the tapered valve opening to balance the pressure differential across the valve as will appear more fully hereinafter. A cap 83 seals the end of the extension 1I.

The regulator section 55 is an annular member having an apertured internal web 84. The section 56 has a plurality of spoke-like members 85 carrying a central apertured hub 86 which is closed at one side by a cap 81.

A regulator control rod is connected to the valve stem 8| by a. double universal joint 9|. Diaphragms 92, 93, 94 and 95 are secured at their central portions to the control rod 90, being maintained in spaced relation by clamping hubs 96. The diaphragms 92 and 94 are respectively secured at their outer edges to the hub 86 and web 84; and diaphragms 93 and 95 are secured at their outer edges between the main sections of the control unit. An annular disc 91 is se-v cured between the sections 54 and 55 and has a finger-like projection 98 to which is riveted a flat spring 99 bearing against the control rod 90 .and urging the valve 19 to the right in a direction to open the valve. A screw |02 is provided in the end of the section 54 and engages the spring 99 for purpose of adjusting the spring force urging the valve open. Guide members |03 are secured to the hub 86 and web 84 and engage the clamping hubs 96 to support and guide the control rod assembly.

The regulator unit C is thus capable of separate assembly, the various sections being held in assembled relation by the assembly bolts 51. The assembled regulator may be tightly clamped in a fixture which holdsl the three sections 54, 55 and 56 securely together and the various chambers checked for leaks. A flange is provided on the throttle body A and a matching flange on the section 56 of the regulator. A plurality of studs ||2 are mounted in the body A and are adapted to receive the assembled regulator C. Nuts I I3 on the studs I|2 hold the regulator unit to the throttle body and also clamp the sections of the regulator tightly together, gaskets being provided at the various surfaces to prevent fuel leakage.

The regulator is thus comprised of six chambers ||6, ||1, IIB, H9, and |2I. Chamber ||1, preferably referred to as the unmetered fuel chamber, is connected to chamber I|6 by means of a fuel pressure transmitting passage |23 and to chamber |2| by means of a fuel pressure transmitting passage |24 drilled in the regulator sections and one of the spoke-like members 85. Unmetered fuel chamber |I1 communicates with the control unit D by means of a fuel conduit |21 which leads from the chamber adjacent the bottom, as indicated at |28 in Figures 1 and 8, through a lower flange |29 (Figure 3) at which the regulator and control units are connected. A vent passage |30 passing through a similar upper flange |3I interconnects theunmetered fuel chamber ||1, adjacent the top as indicated at |32, and the control unit. The chamber II8, preferably referred to as the metered fuel chamber, is connected to the control unit D by means of a fuel passage 34 leading from the bottom of chamber ||8, as indicated at |35 of Figure 2, and passing through the lower flange |29, and also by means of a fuel passage |36 leading from adjacent the top of chamber ||8, as indicated at |31, and passing through the upper flange I3I.

Chamber ||9 1s connected to the air passage 31 in the throttle body by means of air passages 39 and |40 which respectively enter the chamber I|9 adjacent the bottom and top thereof and transmit venturi suction thereto. Chamber ||9 is also connected to chamber |20 by means of a restricted bleed passage |4| located in the bottom portion of the regulator. The previously described air passage 24 leads to the chamber |20 of the regulator unit and transmits air scoop pressure thereto.

The fuel control unit D which is rst assembled and then bolted to the regulator at flanges |29 and I3| is additionally supported by means of a bracket |50 bolted to both the fuel control unit D and the body unit A. The fuel control unit may Vbest be understood from Figures 3 and 8. Fuel is received by the control unit from the regulator unit through the fuel conduit |21 and is delivered to the discharge nozzle adapter section through a fuel outlet conduit |5| and a pipe |52 connected to the control unit at the upper left corner as shown in Figure 3 or at the upper right corner as shown in the diagrammatic Figure 8. The fuel conduit |21 is variably controlled by an idle needle |53 which is moved to the right to restrict the conduit as the throttle I2 approaches closed position. The needle |53, as shown, is a cylindrical member counterbored at one end and having a narrow vertical slot and is adapted to be moved by a lever |54 received in the slot and secured to a rotatable shaft |55 having an operating lever |56 (Figure 1) which is connected by link |51 to a throttle operating lever |58 secured to the throttle shaft I3. An adjustment screw I 59 is provided between the lever |56 and link |51 for adjusting the idle needle position relative to the throttle. A spring |58, the one end of which is received within the counterbored end of the idle needle |53, urges the needle to the right (Fig. 3) to eliminate any play between the needle and lever |54.

The conduit |21 leads into a relatively large fuel chamber |60 in the fuel control unit D. An automatic-lean metering jet IBI connects the chamber I with a chamber 62 having a fuel conduit |63 leading to a chamber |64, the fuel conduit |63 being controlled by a mixture control valve |65 of the disc type which is urged to the right by a spring, not shown. A bleed passage |66 is also provided leading from the top of the chamber |62 to the chamber |64 and is controlled by valve |65. The valve |65 is connected to a rotatable shaft I 68 having an operating lever I 69 attached thereto and is shown in Figure 3 in its idle cut-off" position, a position which is used when the engine is to be stopped. A cuplike member |61 is also secured to the shaft |68 to be rotatable therewith and is provided with an arm |1| connected through a linkage (shown diagrammatically in Figure 8 as a cable) tc the valve 26 in the air passage 25. A spring loaded valve assembly, indicated generally at |12 is received in the bottom of chamber |62 and controls the communication between passage |34 and chamber |62. The valve |12 is operated by a cam |13 on the end of the mixture control shaft |66 and is open at all times except when shaft |68 is in the idle cut-off position.

A power enrichment metering jet |15 communicates the chamber |60 with a small chamber |16. A fuel conduit |11 including an automatic rich metering jet |18 leads from the chamber |16 to the chamber |64 and is controlled by the mixture control valve |65. A fuel conduit |80 leads from the chamber |16 to an economizer chamber I8| which is connected to the chamber |62 by a fuel conduit |82, the chamber |62 communicating with the chamber |64 through port |63 controlled by the valve |65. An economizer valve |83 is spring loaded against a seat |84 and controls the communication between fuel conduit |80 and chamber |8I. The valve |83 has a diaphragm |86 secured thereto which forms a chamber |61 with an economizer cover plate |88. A small bleed passage |89 connects the top of chamber |81 to the passage |30 which leads from the unmetered fuel chamber ||1 to the chamber |64 and is controlled by the valve |65. A passage I9| leads from the bottom of chamber |81 to the fuel conduit |21 from the unmetered fuel chamber I I1.

The mixture control valve |65 is of a contour best shown in Figures 4 to '1 and is operated by the pilot through a link, not shown, connected to the operating lever |88. The valve has four control positions as indicated in Figures 4 to 7. In the idle cut-of! position of Figure 4 the bleed passages |80 and |86 as well as the fuel feeding conduits |88 and |11 are all closed. The valve when in this position cuts off all communication between the unmetered and metered fuel chambers ||1 and |8. In the automatic lean position of Figure 5 the valve |88 only cuts off the conduit |11. In the automatic-rich position of Figure 6, passages |30 and |86 and fuel conduits |88 and |11 are open. In changing from the automaticrich position to the full rich emergency position of Figure 7, no change takes place relative to the passages |30 and |88 and conduits |63 and |11. However, as the lever |68 moves through this increment of travel, the linkage (Figure 8) connecting lever |88 and valve 26 opens the valve 28 in the air by-pass passage 26 around the automatic mixture control unit. The full-rich emergency position, as its name indicates, is used only in an emergency when the pilot desires to eliminate the automatic altitude control accomplished by the bellows controlled valve 41.

After assembly, the fuel control unit D may be separately tested in a test fixture which supplies fuel to conduit |21 at a constant pressure or gravity head. The rate of fuel flow through the unit with the lever |69 in each of its several positions will indicate whether there are any leaks in the casting or whether a metering jet of incorrect size has been used.

The adapter section E (Figure 2) has a flanged inlet o1 a shape adapted to be secured to the outlet flange 202 of the .body A and has an outlet flange 203 of a shape adapted to be secured to the intake manifold of the engine. The adapter may be of the straight through type, the elbow type, the angled type as shown, or of any shape desired. Thus various adapter sections may be used to flt a given carburetor to engines having various types of intake manifolds. A pressure responsive fuel discharge nozzle indicated generally at 204 is mounted in the side of the adapter E and receives fuel from the control unit D through pipe |52 and a, conduit 206 formed in the wall of the adapter E. The fuel discharge nozzle may be of any of the types or arrangements disclosed in the copending application of.Mock and Partington, Serial No. 243,067, filed November 30, 1938, or in my copending application, Serial No. 350,517, filed August 3, 1940. An acceleration pump indicated generally at 2|0 is positioned in the adapter section E and may be of any of the types disclosed in the copending application of Mock and Moore Serial No. 272,990, filed May 11, 1939. The acceleration pump may be assembled as a unit and inserted into the adapter.

Assuming the carburetor has been installed on an engine and does not contain any fuel, the procedure for filling the carburetor, starting the engine, and operating the engine, would be as follows. The procedure for lling the carburetor may best be understood from Figure 8. The mixture control valve is placed in the automatic-rich position, thus uncovering the passages |30, |66, and conduits |63 and |11 and opening the valve |12. Fuel is then supplied to the fuel inlet 88 under positive pressure by means such as a handoperated wobble pump in the fuel line leading from the fuel tank to the inlet 59. The idle spring 99 normally holds the valve 19 off of its seat and therefore allows the fuel supplied to enter chamber ||1 and flow through conduit |21 into the chamber |88. 'I'he fuel rises uniformly in chambers ||1 and |80 until it reaches the Jet |8|. At this time there is fuel in chamber ||1 to the level of the Jet |6| but none in chamber II8. 'I'hel fuel in chamber ||1 urges the diaphragm 88 and attached rod to the left tending to close the valve 18 against the force of spring 88. The level determined by the jet III must be insufficient to close valve 19, otherwise the inflow of fuel would be cut off. Additional fuel entering chamber ||1 flows through metering jet 8|, past valve |12, through passage |34 and into chamber H8. The

fuel level in chamber ||1 thus remains substantially constant until fuel in chamber ||8 reaches the same level. The fuel level then rises uni-l formly in the chambers ||1 and ||8 of the regulator and in the fuel control body. Air which would otherwise be trapped in the top of the chambers ||1 and ||8 of the regulator and of chambers |62 and |81 of the fuel control unit is vented through passages |30, |36, |88 and |88 respectively. As the fuel rises in the units C and D the air is forced out through the pipe |82, from the highest point of the control unit D, to the discharge nozzle. After the device has been filled a small additional quantity of fuel is supplied thereto, causing fuel to deliver from the nozzle 204 for priming the engine to assist in starting.

During operation, the pilot controls the air supplied to the engine and the fuel is controlled automatically as hereinafter described. Air flow through the induction passage creates a differential in pressure between the throat of venturi 28 and the air inlet which is proportional to the square root of the quantity of air flowing. 'I'he venturi suction is transmitted to the chamber ||8 of the regulator through passages 36, 31, 38 and |40. The air inlet pressure is transmitted to the adjacent regulator chamber |20 through tubes I9 and passages 2|, 22, 23 and 24. Venturi suction and air scoop pressure acting on opposite sides of diaphragm 83 create a net force to the right, tending to open the fuel inlet valve 19, which is proportional to the square root of the quantity of air flowing. The sealing diaphragms 94 and 82 are respectively acted on by these two air pressures and merely have the effect of decreasing the effective area of the diaphragm 83 without disturbing the proportional relationship between the air flow and the force on the control rod 80.

Fuel is continuously supplied to the annular chamber 10 under positive pressure by means 0f an engine driven pump, not shown, or from any source of fuel under pressure. The fuel then flows into chamber I|1, through conduit |21 and into chamber |60. If the mixture control valve |65 is in the automatic-lean position of Figure 5 and the engine is operating at a moderate power output, fuel will flow through the automatic-lean metering jet |6I, into chamber |62, through port |83, into chamber |64, through conduit |5|, pipe |52 and conduit 206 t0 the discharge nozzle 204. Fuel in the nozzle 204 urges the diaphragm of the nozzle to the right to open the nozzle valve and allow fuel to discharge into the air fiowing through the induction passage. The fuel pressure in chamber |64 will be less than that in chamber |60 by an amount proportional to the square root of the quantity of fuel flowing through orifice |8|. The unmetered fuel pressure in chamber |60 is equal to that in the unmetered fuel chamber ||1 of the regulator because of the free communication therebetween through conduit |21; and the metered fuel pressure in chamber |84 ls transmitted undiminished to the metered fuel chamber ||8 through passage |36. Thus the.diiferential pressure across metering jet .IBI creating fuel flow is also present across the diaphragm 85 and creates a forcetending to close valve 19 which is proportional to the square root of the quantity of fuel flowing. The unbalanced force normally created by the differential pressure across the poppet valve 19 is balanced out by subjecting the diaphragm 82 connected to the valve to an equal but opposite differential pressure. The control rod 90 will therefore position itself such that the air force and fuel force are maintained equal, thus maintaining a constant proportion between the quantities of air and fuel flowing.

At idle, the idle spring engages the control rod 90 and creates a force, in addition to the air force, tending to open the valve 19 and increase the fuel flow. The idle spring force is of appreciable amount relative to the air force at idle and consequently provides a substantial idle enrichment. air force increase, the idle spring force becomes of lesser relative amount thereby decreasing the idle spring enrichment. As the air flow further increases the rod 90 may move completely off of the spring 99 thus eliminating its effect. It has been found desirable to adjust the idle spring to produce an excessive enrichment at idle and then decrease the enrichment by the throttle controlled idle needle |53 which is adjusted to restrict the conduit |21 at closed throttle and is withdrawn from its restricting position as the throttle moves from its idle position. Any desired enrichment at idle or near idle position may be obtained by the contour and adjustment of the tip of valve N53.

As the air flow and consequently the power output increase, the venturi-to-scoop air pressure differential and the unmetered-to-metered fuel pressure differential will increase. Unmetered fuel pressure is transmitted to chamber |81 by the passage |9| from the passage |21 and acts to the left on the economizer diaphragm |86..

Metered fuel pressure is transmitted to the charnber- |8| through the conduit |82 from the chamber |62 and acts to the right on diaphragm |86. When the differential pressure across the diaphragm |86 reaches a predetermined value the economizer valve |83 opens and allows fuel to ow from chamber |60 to chamber |64 throughV the power enrichment metering jet |15, conduit |80, economizer valve |84 and conduit |82. The regulator C positions the fuel inlet valve 19 to maintain the fuel differential pressure between chambers |60 and |64 equal to the air differential pressure. Since the economizer valve has increased the available fuel metering area, the fuel flow will increase, thus increasing the mixture richness.

If the airplane is now taken to a higher altitude the mixture-to-scoop air differential pressure for a given weight of air will increase. If this increased differential were transmitted to the chambers ||9 and |20 of the regulator the fuel flow would increase and the mixture would become richer with increase in altitude. level the bellows controlled valve 41 has no appreciable restricting effect at the port 48 and air may freely flow from the inlet I0, through tubes i9 into annular chamber |8, through passages 2|, 22. 23 and 24 into the regulator chamber |20, The restricted bleed |4| creates a small flow of air from chamber |20, to chamber H9, through At ground As the air flow and consequently the passages 39, 31 and 36, and discharges into the venturi 29. At ground level, chamber ||9 freely communicates with the venturi 29 and chamber |20 freely communicates with the air inlet I0. The small bleed |4| creates but a negligible effect in disturbing the pressures in chambers H9 and |20. However, as altitude is attained the bellows 45 expands and valve 41 begins to restrict port 48. The bleed |4| then becomes effective to reduce the pressure in chamber |20. The valve 41 is designed to restrict port 48 such that the differential pressure across diaphragm 93 will remain constant for a given weight of air flow regardless of the altitude or the temperature of the entering air, thus maintaining a substantially constant mixture richness with change in altitude.

If the mixture control valve is in the automatic rich position of Figure 6 with the engine operating at but moderate power, the economizer Valve |83 will be closed and the enginewill receive fuel through lthe automatic-lean metering jet ll and also through the power enrichment jet |15, automatic-rich metering jet |18 and conduit |11. The regulator C again maintains the unmeteredizo-metered fuel pressure differential equal to the air differential but the mixture is enriched because of the increased available fuel metering area. Under these conditions the metering jet |15 has very little effect since it is larger than jet |18, the metering thus being accomplished primarily by the jet |15. However, at high power output with the economizer valve |83 open, the jet |15 becomes the primary restriction and the mixture is enriched but very slightly more than at high power output with the mixture control valve in the automatic lean position. 'Ihus the richness of the mixture at high power output is substantially independent of whether the mixture control valve is in the automatic-rich or automatic-lean position, thus insuring that the engine will receive the desired amount of fuel for maximum power and engine safety.

In an emergency at altitude the pilot may obtain additional richness by moving the mixture control valve |65 to the full-rich emergency position of Figure '7. As previously explained, this opens the valve 26 by-passing the altitude control valve 41 and permits the full venturi-to-scoop differential pressure to be transmitted to the regulator, thus increasing the fuel differential pressure and increasing the mixture richness.

From the foregoing discussion it will be apparent that the regulator C merely regulates the drop in pressure across the metering jets and maintains it equal to the venturi-to-scoop differential pressure; whereas the fuel control unit D controls A the available fuel metering area across which the differential pressure is being maintained by the regulator vand therefore controls the mixture richness.

As previously pointed out, both the assembled regulator C and fuel control unit D may be separately tested following assembly. The fuel control unit D is then preferably bolted to the regulator C and the combined assembly tested before installing it on the body section A. Suction from any convenient vacuum source, such as a small vacuum pump, may be applied to chamber l|9 so as to create any desired differential pressure between chambers |9 and |20, the actual differential pressure applied being measurable with a l conventional manometer. Fuel is supplied to the regulator atthe desired pressure and a pressure responsive fuel discharge nozzle, forming a part of the test fixture. is connected to the control unit outlet passage II. The regulator and control unit thus function just as though installed on an engine and operating at a condition at which the air flow created the applied air differential pressure. A fuel ow meter installed in the fuel line indicates the quantity of fuel passing through the regulator and calibration curves of master venturies indicate the air flow corresponding to the applied air differential. Thus the fuel flow and air flow at this fictitious condition of operation may be determined. The fuel metering characteristic of the combined regulator and fuel control unit may thus be checked before installing it on the body unit A.

During operation, vapor may tend to form in the chambers H1 and H8 0f the regulator. As

vapor forms, however, it escapes through the small bleed |30 and passage |31 which respectively enter the chambers H1 and H8 adjacent their uppermost portions. Vapor is thus prevented from collecting in the chambers ||1 and H8 to an extent which would interfere with operation of the device.

When the engine is to be stopped the mixture control valve |65 is moved to the idle cut-off position and the ignition turned off. It should particularly be noted that in the idle cut-off position the valve |65 and valve |12 cut off all communication between chambers H8 and H1. Fuel will continue to enter chamber H1 until the pressure therein increases to a value slightly above that maintained in the metered chamber by the pressure responsive discharge nozzle, at which time the control rod 90 will move to the left overcoming the idle spring and close the valve 19, thereby preventing any additional fuel from entering chamber I1. If the bleed passage |30 or the ll passage I 34 were not closed by the valves |65 and |12, the pressure in chambers ||1 and H8 would equalize and permit the light idle spring to keep valve 19 in open position regardless of how high a pressure was attained in these chambers. Therefore, if the cut-off valve were placed for example in the pipe |52, the pressure in chambers ||1 and 8 would increase to the supply line pressure and tend to cause fuel leakage past the diaphragms.

If the idle cut-off were not provided, fuel Would continue to fiow to the engine at the idle rate until the fuel pressure from the fuel pump dropped below the pressure required to open the valve of the discharge nozzle 204. If the engine is hot at the time the ignition is turned off, the engine might continue to run, due to pre-ignition, if the fuel supply is continued. Furthermore, engine heat after shut down may form vapor in the fuel line leading from the pump which would maintain the fuel supply pressure and cause considerable fuel to leak into the engine manifold and interfere with the next starting operation. These difficulties are overcome by the arrangement of Figure 3.

During periods of inoperation, fuel might slowly -leak past diaphragms 92 and 94 and gradually collect in chambers |20 and I I9 where it would interfere patricularly with starting if no means were provided to eliminate it. Also, water or rain entering tubes I9 might tend to collect in chamber |20. In order to eliminate any liquids collecting in chambers H9 and |20, the passage 39 enters chamber I I9 at its lowermost portion and is provided with a small bleed 38 entering the induction passage posterior to the throttle. 'I'he bleed passage |4| also enters the bottom of chambers H9 and |20. If any water or liquid fuel is present in these chambers the vacuum posterior to the throttle during cranking will draw it out through bleed 30. The passage |40 leading from the passage 31 into the top of chamber I9 is provided to insure that venturi suction will be transmitted to chamberI I9 during starting, even though liquid is present therein which would interfere with the passage 39 transmitting to the chamber I I 9 the moderate starting suctions of but an inch or two of fuel head. During operation a continuous current of Ventilating air passes into tubes I9, through passages 2 22, 23 and 24, into chamber |20, through bleed passage |4I, into chamber H9, through passages 39 and |40, into passage 31, and discharges into the induction passage either through bleed 38 or through passage 30 and annulus 35. Liquids are thus continuously drawn out of chambers H9 and |20 as they collect.

Although the invention has been described in connection with one particular charge forming device it will be apparent that it is applicable to charge forming devices of other types. It will also be apparent that the device disclosed is capable of many modifications and it is not intended that the scope of the invention be limited to the form shown and described, nor otherwise than by the terms of the appended claims.

1. A charge forming device for an internal combustion engine comprising a body unit forming an induction passage having an inlet, a venturi, a throttle posterior to the venturi, and a r fuel discharge nozzle posterior to said throttle;

a fuel regulator unit separably secured to said body section for regulating the quantity of fuel supplied to the nozzle in accordance with variations in the air flow through the induction passage, said regulator including an unmetered fuel chamber, a metered fuel chamber, a depression chamber, an air chamber, a fuel inlet to the unmetered fuel chamber, a valve in said fuel inlet, means responsive to the pressures in said chambers operably connected to said valve, and yielding means urging said valve toward open position; and a fuel control unit separably secured to one of said units for determining the differential in the pressures in the metered and unmetered fuel chambers for a given rate of fuel flow to the nozzle, said control unit including a fuel conduit having a metering orifice therein: said charge forming device includingan air passage leading from the venturi and having a pair of branches respectively entering the depression chamber adjacent the top and bottom thereof, said bottom branch having a restricted connection to the induction passage posterior to theA throttle, fuel passages leading from adjacent the bottoms and from adjacent 'the tops of the metered and unmetered fuel chambers to the fuel conduit, valve means operable to cut off all communication between the metered and unmetered fuel chambers when the engine is to be stopped, and a fuel duct conducting fuel from posterior the metering orifice to said fuel discharge nozzle.

2. A charge forming device comprising a body section forming an induction passage and including an air differential pressure creating means, a fuel nozzle discharging into said passage, a pressure responsive outlet valve in said nozzle, a fuel regulator unit separably secured to the body section and having means for regulating the flow of fuel suppliedA to said nozzle to establish a fuel metering differential pressure variable in response to variations in the air differential pressure, a fuel control unit separably mounted and connected to said regulator unit and including variable area fuel metering means for `varying the quantity of fuel supplied to the nozzle at a given air and fuel differential pressure to thereby vary the richness of the mixture, and means for'sup-` plying fuel at su'peratmospheric pressure to said regulator unit and said control unit.

3. A charge forming device comprising a body section forming an induction passage, a main fuel discharge nozzle discharging into said induction passage, a fuel regulator unit separably secured to the body section and having means for regulating the flow of fuel to said nozzle to produce a fuel metering differential pressure variable in accordance with variations in the rate of air flow through the passage, a fuel control unit separably secured to the regulator unit and having variable area metering means for varying the relationship of the fuel metering differential pressure to the quantity of fuel supplied to the nozzle for varying the mixture richness.

4. A charge forming device comprising the following separable parts: a body section forming an air passage having an inlet and an outlet and including an air differential pressure creating means; a fuel regulator unit secured to the body section and including a fuel control valve and 'pressure responsive means for controlling the valve to produce a predetermined fuel metering differential pressure variable in accordance with variations in the air differential pressure; a fuel control unit secured to said regulator unit and including a fuel conduit, flow restricting fuel metering means in said conduit, and fuel passages connecting said conduit anterior and posterior to said restricting means to said pressure responsive means; and an adapter section having an air passage with an inlet; adapted to be connected to the body section. and a fuel nozzle receiving fuel from said conduit posterior to seid restricting means and discharging into said last named air passage.

5. A charge forming device comprising the following separable parts: a body section forming an air passage having an inlet and an outlet and including a, venturi; an adapter section including an air passage having an inlet connected to said body section outlet and a main fuel nozzle discharging into said adapter section air passage; a fuel regulator section secured to said body section and including a fuel control valve. pressure responsive means for controlling said valve,

and air passages communicating said pressure responsive means with said venturi and said body section air inlet; and a fuel control unit secure-fl to at least one of said sections and comprisinfY a fuel conduit, area restricting means in said conduit, mechanism for varying the effective area of said area restricting means. fuel passages comsaid sections and including a fuel control valve and pressure responsive meansv for controlling said valve; and a fuel control section secured to at least' one of said previously named sections and comprising a fuel conduit, area restricting means in said conduit, and mechanism for varying the effective area of said area restricting means; said sections including .passages forming at least portions of the ducts communicating said pressure responsive means respectively with the venturi, and the conduit anterior and posterior to said area restricting means and of a duct conducting fuel 'from posterior to said area restricting meansto said discharge nozzle.

7. A charge forming device comprising the following separable parts: a body unit forming an air passage having an inlet and an outlet; an

adapter unit secured to said body unit and having an air passage with a fuel discharge nozzle therein; a fuel regulator unit secured to one of said units and receiving fuel from a source, said regulator unit including a fuel control valve and a pressure responsive means for controlling said valve; a fuel control unit secured to at least one of said units and including a fuel passage and means for varying the effective area of said fuel passage; and an automatic mixture control unit secured to one of said units and including a valve and means responsive to variations in barometric pressure for controlling said valve: and conduits connecting said pressure responsive means with the fuel passage and withthe body unit air passage, one of said conduits being controlled by the automatic mixture control unit valve, and a fuel duct conveying fuel from said fuel passage to said discharge nozzle.

8. A charge forming device comprising an induction passage, a fuel conduit discharging into said induction passage, a venturi and athrclttle in said induction passage, means for regulating the flow of fuel through said conduit comprising a pressure cham-ber and a depression chamber, a branched air passage connecting the venturi throat with the upper and lower portions of the depression chamber, a second air passage connecting a point of low suction in the induction passage with the pressure chamber, means responsive to barometric pressure for varying the relative capacities of said air passages` a restricted connection between said chambers, and a drain passage connecting one of said chambers adjacent the lower portion thereof and the induction passage posterior to the throttle.

9. A charge forming device comprising an induction passage, fuel discharging meansfcr discharging fuel into the air flowing through the passage, a fuel conduit supplying fuel to said discharging means, fuel metering means in said conduit for creating a differential in fuel pressures, a pair of air chambers connected to spaced points in the induction passage, a pair of fuel chambers connected to spaced points in the fuel conduit to be subjected to said fuel pressures, means including movable pressure responsive walls in said air and fuel chambers for controlling the flow of fuel to the discharging means. a drain passage connecting the lower portion of one of the air chambers with the induction passage, a restricted passage interconnecting the air chambers at their lower portions, a connection between the lower portions of said fuel chambers, and valve means for closing said connection.

10. The invention defined in claim 9 wherein the charge forming device includes a body portion forming the induction passage, a detachable regulator unit including said air and fuel chambers and adapted to regulate the fuel flow t control the differential/of the pressures in the fuel chambers in accordance with the differential of the pressures in the air chambers, a detachable control unit including the fuel metering means and the said valve means, and a detachable altitude control unit having means responsive to variations in barometric pressure for modifying the relative pressures in the said air chambers.

11.A charger forming device for an internal combustion engine comprising a body unit for creating an air differential pressure variable in response to variations in air flow to the engine comprising an air passage, a venturi, and a throttle posterior to the venturi; a fuel regulator unit separably secured to said body section for varying the fuel now to thel engine to create a fuel metering differential pressure variable in accordance with variations in the air differential pressure comprising a pair of air chambers adapted to be connected to the venturi and air passage anterior to the throttle respectively, a pair of fuel chambers subjected to the fuel metering differential pressure, valve means for controlling the flow of fuel to the engine, and diaphragms subjected to the pressures in said air and fuel chambers for actuating said valve means; and a fuel control unit separably secured to the regulator unit for varying the quantity of fuel supplied to the engine at a given fuel metering differential pressure comprising a fuel conduit transmitting fuel supplied to the engine, area restricting means in the conduit for creating the said fuel metering differential pressure, manual means for varying the effective area of the area restricting means, and means for automatically varying the effective area of the area restricting means.

l2. The invention defined in claim 1l comprising in addition an automatic mixture control unit separably secured to the body unit for varying the richness of the mixture in response to variations in pressure resulting from change in altitude comprising a sealed capsule, and a valve controlled by said capsule and operative to modify the pressures in the air chambers.

13. A charge forming device for an internal combustion engine comprising a body unit forming an induction passage having an inlet, a venturi, a throttle posterior to the venturi and fuel discharging means posterior to the throttle; a fuel regulator unit separably secured to said body section for controlling the fuel metering differential pressure including a fuel valve for regulating the flow of fuel. and pressure responsive diaphragms connected to said valve and adapted to form movable walls of an unmetered fuel chamber, a metered fuel chamber, an air chamber and a depression chamber; and a fuel control unit separably 4secured to one of said units for varying the quantity of fuel supplied to the engine at a given fuel metering differential pressure including a fuel conduit, area restricting means in said conduit for creating the fuel metering differential pressure, and means for varying the effective area of said area restricting means: said charge forming device including an air passage leading from the venturi and having a pair of branches respectively entering the upper and lowermost portions of the depression chamber,

the latter having a restricted connection to the induction passage posterior to the throttle, and fuel passages leading from adjacent the bottoms and adjacent the tops of the metered and unmetered fuel chambers to the fuel conduit.

14. In liquid fuel control apparatus for an internal combustion engine, a fuel conduit for supplying fuel to the engine and including fuel metering means, a pair of fuel chambers communicating with the fuel conduit anterior and posterior to the fuel metering means, each of said chambers having a movable wall, means controlled by movement of said walls for regulating the flow of fuel through the conduit, a connection between the lower portions of said chambers to permit simultaneous filling of the chambers, an element operable from a point remote from the apparatus, and means actuated by said element for varying the effective area of said fuel metering means and for opening and closing said connection.

15. In liquid fuel control apparatus for an internal combustion engine, a fuel conduit for transmitting fuel to the engine, means in the conduit for creating a differential in the pressures at spaced points in the conduit, two fuel chambers respectively in communication with the conduit at said spaced points, each of said chambers including a movable wall, a valve in the conduit controlled by movement of said walls for regulating the flow of fuel through the conduit, a connection between the lower portions of the chambers, a vent passage from the upper portion of at least one of said chambers to the fuel conduit posterior to the valve and posterior to at least one of said spaced points, and means operable from a point remote from the device for opening and closing said connection and said vent passage.

16. In liquid fuel control apparatus for an internal combustion engine, a fuel conduit for transmitting fuel to the engine, a pair of fuel chambers freely communicating with said conduit at spaced points, each of said chambers having a movable pressure responsive wall, valve means controlled by movement of said walls for regulating the flow of fuel through said conduit, yield ing means urging said valve means in a direction to increase the fuel flow, fuel metering means in the conduit for creating a differential between ythe pressures at said spaced points, means including said conduit and additional passages for intercommunicating the upper portions of the chambers and the lower portions of the chambers respectively to thereby permit simultaneous filling of the chambers, and valve means operable from a point remote from the engine for closing said intercommunicating means to thereby cut off all communication between said chambers.

17. In a fuel control system for an internal combustion engine having an air supply duct, a venturi in the duct, a throttle in the duct posterior to the venturi, a fuel conduit for supplying fuel to the engine, an air chamber, a depression chamber, an unmetered fuel chamber, a metered fuel chamber, each of said chambers including a movable wall, means operably connected to said movable walls for controlling the flow of fuel through the conduit, an air passage leading from the venturi and having a pair of branches respectively entering the depression chamber adjacent the top and bottom thereof, an air passage leading from the air supply duct anterior to the throttle to the air chamber, an air passage interconnecting said air and depression chambers, means responsive to variations in barometric pressure for controlling the relative capacities of said air passages, a restricted connection between the air supply duct posterior to the throttle and the lower portion of one of said air chambers, means intercommunicating the upper portions of the unmetered and metered fuel chambers, the lower portions of the unmetered and metered fuel chambers, and communicating the unmetered and metered fuel chambers with the fuel conduit, and means operable to cut off all communication between the unmetered and metered fuel chambers when the engine is to be stopped.

18. A fuel feeding system for an internal combustion engine comprising an air passage for supplying air to the engine, a throttle in said passage, a venturi in the passage anterior to the throttle, a fuel conduit for supplying fuel to the engine, means for regulating the iiow of fuel through said conduit comprising a pressure chamber and a depression chamber, passages connecting the venturi adjacent its throat with the upper and lower portions of the depression chamber, another air passage connecting the pressure chamber to the induction passage anterior to the throttle at a point of low suction, a restricted connection between said pressure and depression chambers, and a drain passage connecting one of said chambers adjacent the lower portion thereof and the induction passage posterior to the throttle.

19. A charge forming device for an internal combustion engine comprising the following separable parts: a body unit forming an air passage having an inlet and an outlet and including a differential pressure creating means; a fuel regulator unit separably mounted and receiving fuel from a source, said regulator unit including a fuel control valve and pressure responsive means for controlling said valve; a fuel control unit separably mounted and including a fuel passage and means for varying the effective area of said fuel passage; and an automatic mixture control unit secured to one of said units and including a valve and means responsive to variations in barometric pressure for controlling said valve: and conduits connecting said pressure responsive means respectively with the fuel passage, the air passage, and the differential pressure creating means, one of said conduits being controlled by the automatic mixture control unit valve, and means including a fuel duct for conveying fuel from said fuel passage to the engine,

20. A charge forming device for an internal combustion engine comprising a body unit form ing an induction passage and including an air differential pressure creating means and a throttle posterior thereto; a fuel regulator unit separably secured to the body section and having means for regulating the ow of fuel to the en1 gine to produce a fuel metering differential pressure variable in accordance with variations in the air differential pressure; a fuel control unit separably secured to the regulator unit and hav ing variable area metering means for varying the relationship of the fuel metering differential pressure to the quantity of fuel supplied the engine for varying the mixture richness; and an automatic mixture control unit separably secured to one of the units for varying the richness of the mixture in response to variations in pressure resulting from change in altitude comprising a calibrated passage, a valve cooperating with said passage for varying the effective area thereof to modify the quantity of fuel supplied to the engine, and a sealed capsule for operating said valve.

FRANK C. MOCK. 

